Molding composition and method of treating



4 Patented Mar. 21, 1933 Georgia. white clay, or the like,

UNITED STATES PATENT OFFICE BOY A. PLANT AND IAITLEY E. BROOKS,

DOW CHEIIOAL comm, OI MIDLAND,

MICHIGAN, ABBIGNOBS ,10 THE MICHIGAN, A CORPORATION OI MICHIGAN HOLDING GODOSITION AND I'ETHOD 01' HEATING Io Drawing.

The present invention relates to the treatment of molding compositions and specifically to the treatment of such compositions to reduce or eliminate to a large extent loss of moisture from the composition prior to the pouring of a casting into a mold formed therefrom. It is well known that molding compositions, such as water moistened green sand, tend to dry out fairly rapidly. In order .to keep such compositions in proper temper for use, the common procedure is to moisten the surface of the heap of molding sand, cover it with a wet canvas, or else moisten and rework the sand at relatively frequent intervals. Of recent years synthetic molding compositions utilizing bentonite,

as a plasticizer, have been coming more and more into common use. These synthetic compositions likewise present the same drying out problem as is encountered with natural compositions, although ordinarily to a slightly lesser degree which is possibly due to efficient mixing and the use of plasticizers which retain moisture slightly better than positions. The drying out difiiculty is'not only encountered in keeping the composition in proper temper for molding but is also present after the mold is made up s nce, if the mold is left open, the surface dries out, especially the sharp edges, leaving the surface in a condition susceptible to washing when the metal is poured in contact therewith. We have now found that the addition of certain hygroscopic materials to the molding composition, either natural or synthetic, either eliminates or greatly reduces the drying out tendency that has heretofore been considered .anecessary evil by those familiar with the art.

To the accomplishment of the foregoing and related ends, the invention, then, consists of the method, steps and product hereinafter fully described and particularly pointed out in the claims. the 0 lowing description setting forth in detail several forms of product and modes of carrying out the invention, such disclosed forms and I modes illustrating, ever, but several of the variouswaysin who the principle of the invention may be used.

how-

Applioaflon fled July 80,

those in natural com- P h of time with l1ttle 1981. Serial Io. 554,154

In the working up of the molding composition according to our invention, the hygrd scopic salt may beadded directly thereto or dissolved in water or the like and then added to the molding sand, the whole having sufficient water admixed thereto to temper it to a -magnesium chloride and calcium chloride or mixtures of them are noted. The latter three, which are of a deliquescent nature, we have found to be highly satisfactory for most puroses.

which is commonly known as a solution of calcium, magnesium, and sodium chlorides, can in general be used in equivalent manner to the salts above noted, limiting factors being the strength of the solutionin desired hygroscopic halogen salts and the amount of water required by the composition. These materials may be added witha desirable effect to the molding composition in amount (halogen salt basis) rangin from 1 to10 per cent of the composition, a though for most purposes approximately 4 per cent gives sat1sfactory results. Where either a. natural molding composition, or a synthetic composition consisting of a mixture of sharp or bank sand with 2 to 10 per cent of bentonite or its equivalent as a plasticizer, is used for molding,

- we prefer to add approximately 4 per cent of calcium chloride to the composition to overcome its drying out tendency. Such composition, after initial tempering and mixin preferably in a Muller type of ap aratus, wi retain its tem er for relatively ong periods or no further attention. Recently considerable work hasbeen done Natural brines such as bitter water position to prevent excessive with a synthetic carbon base molding composition for use in casting readily oxidizable materials, such as magnesium and its alloys.

his composition, which consists specifically of a mixture of pulverized carbon 86 per cent, bentonite 3 per cent, oxidation inhibitor (boric acid, sulphur, or ammonium compounds including ammonium chloride or ammonium sulphate) 4 per cent, water 7 per cent, tends to dry out very rapidly. The treatment of this composition with approximately 4 per cent calcium chloride, we have found substantially overcomes the drying-out tendencies of this composition and, moreact in a detrimental manner to accelerate oxidation of the readily oxidizable metal cast. The use of our improved procedure in connection with synthetic'molding compositions, such as those made from sand or carbon, further appears to have a marked eliect in reducing the amount of agent, such as bentonite, necessary to give the molding composition sufficient bond to mold properly.

The term molding composition as used in the claims is to be understood to cover both natural molding compositions and synthetic compositions. In like manner, the term finely divided base material isto be considered to cover sand, pulverized carbon, pulverized cinders, etc., usable as the base material in a molding composition.

Other modes of applying the principle of our invention may be employed instead of thoseexplained, change being made as regards the method and product herein disclosed, provided the method and product stated in any of the equivalent thereof be employed.

We therefore particularly point out and I distinctly claim as our invention 1. In a method of treating a molding composition to prevent excessive loss of moisture, the step which consists in incorporatlng in such composition a. hygroscopic, fluorine free, halide salt.

2. In a method of treating a molding composition toprevent excessive loss of moisture, the step which consists in incorporating in such composition 1 to scopic, fluorine free, halide salt.

3.- In a method of treating a molding comloss of moisture, the step which consists in incorporating in such composition 1 to quescent, fluorine free, halide salt.

4. In a method of treating a molding composition to prevent excessive loss of moisture, the step which consists in such composition 1 to 10 deliquescent chloride.

5. In a method of treating a molding composition to prevent excessive loss of moisture, the step which consists in incorporating in per cent of a I such plasticizing composition to following claims or the 10 per cent of hygro- 10 per cent of deliacoaeae such composition 1 to 10 per cent of calcium chloride. 6. In a method of treating a molding composition to prevent excessive loss of moisture, the step which consists in inco crating in composition approximately 4 per cent of calcium chloride- 7. A moldin composition comprising a finely divided base material, a plasticizer, l to 10 per cent of hygroscopic, fluorine free,

halide salt, and suflicient water to moisten the mixture and render same moldable.

8. A molding composition comprising pulverized hard carbon, a plasticizer, and 1 to 10 per cent of hygroscopic halo on salt, the w ole being moistened with so cient water to render same moldable.

9. A molding composition-{consisting of pulverized hard carbon, bentonite, and 4 ercent of calcium chloride, the Whole being moistened with sufficient water to render same moldable.

10. A molding composition comprising sand, a plasticizer, and 1 to 10 per cent of hygroscopic, fluorine free, halide salt, the Whole being moistened with suflicient water to render same'moldable.

11. A molding composition consisting of bank sand, bentonite 2 to 10 r'cent, calcium chloride 1 to 10 per cent, andiufiicient water to render the mixture moldable.

12. In a method of treating a molding I revent excessive loss of moisture, the step w ich consists in incorporating in such composition at least one of the halide salts calcium bromide, magnesium bromide, lithium bromide, lithium chloride, magnesium chloride, calcium chloride, double chloride of calcium and magnesium.

13. A mold composition comprising a fine- 1y divided base material, a plasticizer, 1 to 10 per cent of calcium bromide, magnesium bromide, lithium bromide, lithium chloride, magnesium chloride, calcium chloride, double chloride of calcium and magnesium, and suificient water to moisten the mixture and render same moldable.

Signed by us'this 28th day of July, 1931.

ROY A.PLANT. MANLEY E. BROOKS.

incorporating in g at least one of the halide salts 

